1. Field of the Invention
The present invention generally relates to 3-dimensional scanning, and, more particularly, to a portable 3-dimensional scanning apparatus for hand-held operations.
2. Description of the Prior Art
In the field of information sensing, machine vision technologies provide valuable information about the environment and about specific objects of interest through close inspection. Known 3-D data acquisition systems have been provided using 3-D sensors based on the active triangulation principle. In such systems, a specific known and fixed pattern of illumination (i.e. structure illumination) is projected from a laser and optical arrangement on an object to be measured, and the intersection of that emitted pattern is observed from a known and fixed oblique angle by a digital camera, such as a charged coupled device (CCD) array, whereby the position of the illuminated points on the object translate to positions on the camera array and the position of the illuminated points on the object can be computed trigonometrically.
For instance, one of these systems is referred to as a laser profilometer, wherein as indicated, a laser beam is used for illumination. Such profilometers analyze deformations of a laser line on an object such as to evaluate, for instance, the depth (Z-axis) as well as the horizontal position (X-axis) of the object. Generally, the translation of either one of the profilometer and the object to be scanned with the help of a translation mechanism allows to obtain the missing vertical position (Y-axis). Consequently, a 3-D profile of the object is scanned.
The above described system is widely used in industrial environments whereat the objects to be scanned are conveyed, whereby no translation mechanism is required with the profilometer. However, this system is not as convenient when, for instance, the object to be scanned is idle and/or hard to displace. In such cases, it is necessary to move the profilometer. In the event where the piece is large and/or defines a complex shape, it may be complicated to move the profilometer with the help of a simple translation mechanism. Thus, the use of a robot is often required, thereby entailing an increase in costs and often a decrease in precision.
A versatile 3-D data acquisition system would allow to digitize without contact the 3-D shape of an object while computing the absolute position and orientation of its scanned points, thus giving an operator, in different instances, the freedom to manipulate the system as if he was painting the surface of this object. The gathered 3-D data could, for instance, be used offline for the update of a work site model or for close and specific inspection of the shape integrity of objects compared to their CAD models.
It is therefore an aim of the present invention to provide a profilometer trackable in a volume space for 3-D data acquisition.
It is a further aim of the present invention to provide a 3-D data acquisition system having a compact and portable scanner portion.
It is still a further aim of the present invention to provide an improved method for 3-D scanning of objects.
Therefore, in accordance with the present invention, there is provided an apparatus for three-dimensional scanning, said apparatus being manually maneuverable and comprising a profilometer including a light beam projector, an objective and a light detector, said profilometer configured for obtaining a two-dimensional profile of an object by active triangulation; and a positioning device being trackable in a volume space for providing six degrees-of-freedom of said apparatus; whereby a three-dimensional profile is calculatable by relating the two-dimensional profile with time-corresponding positions and orientations of said apparatus.
Also in accordance with the present invention, there is provided a system for three-dimensional scanning, comprising said above described apparatus, and further comprising a three-dimensional profile calculator remote from said apparatus for tracking said apparatus in said volume space and relating positions and orientations of said apparatus with a time-corresponding two-dimensional profile of the object for calculating a three-dimensional profile thereof and for referring the object to a static position and orientation.
Further in accordance with the present invention, there is provided a method for three-dimensional scanning, comprising the steps of (i) scanning a two-dimensional profile of an object with a profilometer projecting a light beam on the object and using active triangulation; (ii) tracking said profilometer in a volume space for obtaining positions and orientations thereof; and (iii) calculating a three-dimensional profile of the object by relating time-corresponding two-dimensional profile and positions and orientations.